Automatic and semiautomatic telephone exchange



April 13 1926.

N G. PALMGREN AUTOMATIC AND SEMIAUTOMATIC TELEPHONE EXCHANGE Filed Dec 22. 1923 7 Sheets-Sheet 1 r I n v01 for" N175- GU/mm Palm gr'gn April 13 1926.

N. G. PALMGREN AUTOMATIC AND SEMIAUTOMATIC TELEPHONE EXCHANGE Filed Dec. 22, 1923 7 Sheets-Sheet 2 o oqo o o A ril 13 1926. 1,580,321

N. G. PALMGREN AUTOMATIC AND SEMIAUTOMATIC TELEPHONE EXCHANGE April 1-3, 1 .6.

N. G. PALMGREN AUTOMATIC AND SEMIAUTOMATIC TELEPHONE EXCHANGE Filed Dec. 22, 1923 '7 Sheets-Sheet 4 Q3: Ni/S GunnarBz/mgren I n vemfor' N. G. PALMGREN Filed Dec. 22.: 1923 April 13 1926.

AUTOMATIC AND SEMIAUTOMATIC TELEPHONE EXCHANGE April 13 1926..

N. G. PALMGREN." AUTOMATIC AND SEMIAUTOMATIC TELEPHONE EXCHANGE Filed Dec. 22. 1925 7 Sheets-Shee t e In yew/or Ni/s G 1 7 N NM n a g g, 0 m 1 a S 11 m m A n w W 7 \MQ E I m H N m 3 U E L w R W 1 H G C 5 M .I 2 1 L T 2 I. A m c L P m. e if I U D G W m N w m a? w a A C Q R I 6 M m fi E y a mo; u N Sm 6 w k & k l w Q i R 1 $Mfi 3 R i 1 w ll. g R E M w M w w xwfiwwmmw 4m a \NMN l'nyenfoj I N Gun/101F1 0 og! lmoren Patented Apr. 13, 1926.

UNITED STATES 1,580,321 PATENT OFFICE.

NILS GUNNAB PALMGREN, OF STOCKHOLM, SWEDEN, ASSIGNOB TO ALLMKNNA TELE- FONAKTIEBOLAGET L. M. ERICSSON, OF DOBELNSGATAN, STOCKHOLM, SWEDEN.

AUTOMATIC AND SEMIAUTOMATIC TELEPHONE EXCHANGE.

Application filed December 22, 1923. Serial No. 682,184.

Toa'll whom it may concern Be it known that NILS GUNNAR PALM- GREN, a subject of the King of Sweden, rcsiding at 1% Varvsgatan, Stockholm, Sweden, has invented certain new and useful Improven'icnts in Automatic and Semiautomatic Telephone Exchanges, of which the following is a specification.

The invention relates to automatic and semiautomatic telephone-exchanges, in which.

the selective operation of the numerical selectors is controlled by a register equipment which has been previously set in accordance with the number of the wanted subscriber by means of current impulses sent from the subscribers station or an operators position respectively. The object of the invention is to prevent disturbances and wrong connections which may be caused by the numerical selectors and the register switches not operating exactly in the same tempo what may occur for lnstance when the numerical selectorsoperate at a great speed, in which case oneor more of the current impulses sent to the" register switches may be lost. It may also occur that the time intervals between the current impulses is too short toallow the stopping device of the numerical selectors to operate exactly in the right moment, thus causing the selector to pass the contact position in question. In ac-' cordance with this invention said inconveniences are overcome by the current mpulses for setting the numerical selectors and theregister switches being sent alternately from the register switch to the selector and from the selector to the register switch, over circuits which are controlling one another in such a way that the selector cannot be set into a new position until'the register switch has been advanced into a corresponding position.

Another object of the invention is to attain a great speed of operation of the numerical selector and the register switches notwithstanding said mutual control which otherwise might cause some delayin the switching operation. To this end a particular kind of selector switches and, contingently, also register switches are used in accordance with this invention, which are so devised as to be advanced two steps for each current impulse, viz, one step upon the closure of the impulse circuit and another step upon the opening of the impulse circuit. In

using such switches preferably only every second posit on of the switch is used for numerical des1gnation, the intervening positions being utilized for sending out control lmpulses to the register equipment or the selector respectively.

The lnvention is not limited to systems using mechanical selectors and register switches as switches made up entirely of relays may also be used. Primarily, however, the nvention contemplates the use of mechanical switches and, particularly, switches of. the kind which are driven during the selective operation by spring power or the l ke and which are stopped in different posltions of adjustment by means of a holding magnet. It has proved in practice that switches of this type are capable of a considerably quicker operation than such' electro-mechanical switches in which the electro-magnet forms at the same time the pro-- polling device of the switch.

' The invention will be more closely described with reference to the accompanying drawings. Fig. 1 is a simplified circuit diagram illustrating the principle of the invention. Fig. 2 shows the construction of the numerical selector switches. Figs. 3-8 represent a complete circuit diagram for a talking connection in a semiautomatic telephone-exchange according to the invention, Fig. 3 showing the line finders and the preselectors, Fig. 4 one of the first group selectors and the appertaining junction finder and sequence switch, Fig. 5 the register finder, the register equipment and the appertaining control switches, Fig. 6 one of the second group selectors and the appertainin junction finder and sequence switch, Fig. l the connector and the appertaining sequence switch, and Fig. 8 the line selector and the appertaining selector finder and switching relays.

In Fig. 1 FL designates a junction line leading into the first group selecting section, said junction line being connected to the subscribers line in known manner by means of a line finder and a pro-selector.

The figure shows schematically three register switches RE RE RE forming together a register equipment REG. A number of such register equipments are accessible in common to'a group of junction lines FL over register finders RSG, one such registerfinder being allotted to each junction li ne FL. The successive connecting of the different register switches to the junction line FL or the numerical selector RV respectively is effected by means of a primary register controller PRO and a secondary register controller SRO respectively. Connected to the junction line FL is an impulse rela RS adapted to be included in the subscribers line circuit and to transmit the impulses from the subscribers station to the register switches.

The construction of the numerical selector RV schematically illustrated in Fig. 1, will appear from Fig. 2. The selector is of the electro-mechanical type above referred to, the movable contact arms SK of which are adapted to be advanced by the action of a spring KF under the control of holdlng magnet R. The contact arms SK are carried by a shaft VA and mounted in hearings in the switch frame. Rigidly secured to said shaft is a ratchet segment ST arranged to' co-operate with a double holding pawl VH pivotally mounted on a pin HT and actuated by a spring HF. Sald pawl is adapted to be operated by one end of the armature MA which is pivoted on an edge MT. The spring KF is fixed at one end to the frame by means of a screw MS and at the other end to a roller FR fixed on the shaft VA. It will be understood from the figure that the contact arms SK are advanced in the direction of the arrow one step upon the magnet R attracting its armature, and another step upon the magnet releasing its armature. After the contact arms have been displaced in this way into the last position, they will be restored to the initial position, which is the first contact position, by means of a lever (not shown in the drawing) swingable about an axis co-axial with the shaft VA and adapted to engage the projection AV of the ratchct segment AT so as to turn the latter back into the initial position.

As seen from Fig. 1, the numerical selector RV has three rows of contacts RK RK RK Arranged to co-operate with these contact rows are three corresponding contact arms consisting of contact springs adapted to connect the opposite contacts of each particular row in each position of the selector.

In the example shown in Fig. 1 the register switches RE are supposed to be constructed in the same way as the numerical selector-s, but they are accommodated for only one row of contacts. The different numerical positions of the contact arms are indicated by means of dot-and-dash lines and are designated in the register switches by figures in the order of sequence 1, 2, 3 0, and in the numerical selectors by figures in the order of sequence 0, 9, 8 1. Between said numerical positionsthere are intermediate positions through which the contact arms have to pass for the purpose of the mutual control of the selective operation.

In the system represented in the drawings each junction line F L is provided with a group selector RV serving only to mark the i group of junction lines L to which the connection is to be extended, the connections between the junction lines being established by means of separate connecting apparatus b which in this case are arranged to operate as finder switches. The group selector RV may, contingently, be arranged in known manner in common to a plurality of unction lines. The invention is not limited to systems wherein the numerical selectors form independent switching units separated from the connecting apparatus, as it is readily understood that the invention may be applied also to systems in which the numerical selectors serve at the same time to establish the talking connections.

The switching operations are controlled in known manner by means of sequence switches regulating the order of sequence of the different operations. In Fig. 1 a sequence switch SOG is indicated serving to control a number of contacts SO adapted to be closed in those positions of the sequence switch indicated by numerals placed close to the contacts.

The switching operation is, shortly stated, as follows. When the calling subscribers 11118 15 connected to the junction line FL the register finder RSG is started whereby a disengaged register equipment REG is connected to the junction line in question.

The subscriber then operates his impulse sender thereby causing the relay RS to energize and de-energize alternately, a corresponding number of current impulses being then sent to the register switch RE over the primary register controller PRO 'iI1 its first position. The register switch RE is thereby set into a'position corresponding to the number of current impulses while being advanced one step foreach closure of the circuit and another step for each interruption of the circuit. A series of impulses corresponding to the first digit of the numher having thus been sent, the register controller PRO will be operated so as to cause thenext series of impulsesto be received by the second register switch RE which is then set in a similar way. Similarly also the other register switches will be set by the following impulses sent from the subscribers station.

The starting of the group selector RV takes place immediately after the first register switch RE having been set. the sequence switch SOG being then advanced into its third position in which the magnet R of the group selector is connected in circuit through the contact S0 and through contacts of the register switch RE At the same time a circuit is closed for a slowacting relay RST through contacts of the group selector RV in its first position said relay then attracting its armature and causing the sequence switch SOG to be moved into its fourth position. Upon the magnet R attracting its armature, the contact arms of the group selector are advanced into the second position in which a circuit is closed through the holding magnet of the register-switch RE, the switch last mentioned being thereby advanced into an intermediate position in which the impulse circuit of the group selector is opened. The group selector will then take another step forward thereby opening the circuit of the register switch which. consequently. will be advanced another step into the next numerical position in which the circuit of the group selector is closed so as to cause the group selector to take another step forward. In this way the switchingoperation will be going on while breaking and closing the two impulse circuits alternately, until the register switch RE reaches the position fol lowing immediately after the last numerical position and in whichthe magnet of the group selector receives another current impulse before having dropped its armature. The contact arms of the group selector will, consequently, be retained in the corresponding intermediate position. The slow-acting relay RST. which has kept its armature attracted during the setting of the group selector due to the current impulses received through contacts of the contact row RK in every second position of the selector. will now be. vie-energized. In releasing its armature it closes a circuit through the sequence switch SOG which is thereby advanced into its fifth position. The circuit of the group selector is then opened at the contact S0 and the group selector will, consequently, be moved into the next numerical position in which a circuit is closed through the clutch magnet KM for a number of junction finders S appertaining to the numerical group selected. said junction finders being thereby started simultaneously to search the junction line FL in question. The junction finder which first finds said junction, will establish the connection at the same time causing the other junction finders to be stopped. lVhen the junction finder is connected to the junction line, a circuit is closed over the c-wire of the junction through the slow-acting relay RST which then again attracts its armature and causes the sequence switch SOG to be advanced into the sixth position in which-the register equipment REG is connected to the junction line FL through the contacts S0 and S0 At the same time the secondregister controller SRO will be operated to cut off the firstregisterswitch RE and to cut in the second register switch RE the next group selector being then set in a similar way by current impulses which are sent alternately from the register switch to the group selector and from the group selector to the register switch over two corresponding circuits which in this case are carried over the two line branches a and I). After the second group selector having been set, the other group selectors and, finally, the line selector are set in a similar way under the control of the register equipment the switches of which are connected up successively by the controller SRO.

The system shown in Figs. 3-8 differs from the arrangement shown in Fig. 1 by the impulse circuits of the numerical selectors not being controlled by contacts of the register switches but by a control relay RR Fig. 5, operated from the selector and arranged to control a local circuit of the holding magnet of the register switch. The object of this arrangement is to reduce the number of contacts of the register switches as In this case no contacts are required on the register switches except in their end positions. At the same time the mechanical motion resistanceis reduced to such an extent that the register swltches will ope-rate equally rapidly and reliably as ordinary relays. The speed of operation will therefore be dependent exclusively on the speed at which the numerical selectors are operating.

The prlmary and secondary register controllers PRO and SRO are of the same construction as the register switches and the numerical selectors. The returning of the contact arms of the register switches and the register controllers to the normal position (the first contact position) is effected by means of a machine driven switch MR, Fig. 5, which serves at the same time as a sequence switch 'for controlling certain switching operations. The returning of the contact arms takes place, when said switch is moving from its third position back into its first position a rotating arm of the switch then operating the ratchet segments ST, Fig. 2, of the different register switches and controllers in the manner above described, to carry the contact arms into the normal position. The different group selectors RV,, RV are restored to normal position in a similar way by the appertaining sequence switches SOG and SOG respectively.

The line finder S and .the pre-selectors S Fig. 3, as well as the junction finders tion of a disengaged junction line being effected by the co-operation of several finder switches in such a. way that a plurality of switches are started simultaneously to hunt for the junction line in question the connection being established through the switch which first finds said junction. In the example shown the finder switches are of the machine driven type having rotary motion in one direction only. Each finder switch is provided with a clutch magnet KM by means of which the contact arms are coupled in known manner to a continuously rotating shaft.

The connecting apparatus S Fig. 7, of the last connecting section are of the same construction as the other finder switches and are likewise arranged to operate as searchers, the selecting and marking of the subscribers line wanted being effected by means of separate line selectors LV, Fig. 8, which are accessible in common to a group of junction lines FL and provided with finder switches LVS by means of which an idle line selector LV is automatically connected to the junction line in question. Each line selector comprises a tenth selector LV- and a unit selector LV which are of the same construction as the group selectors and which are restored to normal position by means'of a sequence switch MRV.

The complete switching operation is as follows. Upon a call on the subscrlbers line AL, Fig. 3, a circuit l'is closed as usual through the line relay LR, which in turn closes a circuit 2 through a relay CR, common to all subscribers lines of the appertaining line group. At the same time a test potential is connected through a contact K to the c-wire of the subscribers line. Supposing there is no ple-selector connected up to a disengaged junction line at the time, the relay CR will close a circuit 3 through the clutch magnet KM of all accessible preselectors S of the group in question said pre-selectors being then started at a time.

As soon as a pre-selector finds a disengaged junction line FL a circuit 4 is establlshed over the d-wire, a relay DR belonging to the pre-selector S in question being then operated to disconnect; the clutch magnet KM whereby said selector is stopped on said junction line FL.. The circuit 4 also includes a relay RS Fig. 4, by which a test potential is connected to the c-wire of the line ML. When the relay DR energizes. a resistance \V, connected in series therewith will be shortcircuited, whereby the junction line FL is marked as engaged for all other pro-selectors S At the same time as the pre-selector S is caused to sto the corresponding line finder S, is started over a circuit 5 including the clutch magnet KM of the line finder. According as other pro-selectors S are connected to disengaged junction lines, the corresponding line finders S will also be started in a similar way. A plurality of line. finders may thus be operating all at a time. That one which first finds the calling subscribers line, will close a circuit 6 through a relay ER appertaining to this line finder, said relay then attracting its armature and opening the circuit of the clutch magnet KM, of the line finder, whereby the line finder is stopped. The circuit 6 also includes the subscribers cut-off relay BR which, in locking itself over a contact K disconnects the line relay LR whereby also the relay GR is deenergized. The circuits of the other line finders S will, consequently, be opened at the contact K,,. At the same time the operating circuits of the pre-selcctors S which are still working are opened at the corresponding contacts K Relay ER, upon energizing, will shortcircuit a resistance W connected in series therewith, for the purpose of preventing disturbances by other pie-selectors which may make contact occasionally with the junction line in question. Further, the relay ER will cause a relay GR to be energized whereby the talking line branches will be switched on to the junction line FIJI, the subscribers microphone circuit will then be closed through the two windings of a relay RS Fig. 4;, which will keep the relay RS and thereby also the relay ER energized over its contact 7 after the circuit 4 has been opened at the contact K,; of the relay GR.

The relay RS upon energizing, closes a circuit 8 through the clutch magnet KM of the sequence switch SOG,. whereby the sequence switch is advanced into the second position while being centered in proper position by means of a contact spring KF in well-known manner. tion of the sequence switch a circuit 9 is closed including the clutch magnet KM of the register finder 'R-SG, whereby the latter is started to connect the junction line FL to an idle register equipment REG, Fig. 5. Upon the register equipment being connected up, a circuit 10 is closed including a relay RS Fig. 4, which operates to disconnect the clutch magnet KM of the register finder and to energize a relay RS over a circuit 11 whereby connection is established between-the'junction line and the register equipment. At the same time the circuit 12 is closed whereby the sequence switch SOGr is advanced into its third position. Said circuit 10 also includes a relay RR,, Fig. 5, which operates immediately upon the junction line being connected to the register equipment thereby causing a circuit 13 to be closed through the clutch magnet KM, of the sequence switch MR which will then be moved into its second position in which the relay RR, receives holding current over the In the second posicircuit 14. The relay RR also closes a circuit 15 through a slow acting relay RR,

which in turn'closcs a circuit 16 through the holding magnet IM of the primary register controller PRO- which will thus advance one step. The circuit 15 is thereby opened and the relay RR- will theretoietie-energize. thereby disconnecting the magnet 1M, and causing the register controller to be advanced one step further. In this position of the register controller a buzzer circuit 13 is closed including a buzzer generator SU and a winding SL of the relay RS Fig. 4. A calling subscriber will thus obtain a buzzer signal to indicate that the subscriber may now-start the sending of the selective current impulses.

hen the sequence switch SOG,, Fig. 4, was moved into the third position, a circuit 18 was closed through a slow actingrelay RS whereby a circuit 19 was closed causing the sequence switch to be advanced into the fourth position, which position the sequence switch will thus occupy, when the subscriber begins to send out the selective current impulses.-

iVhcn the subscriber now operates his impulse sending apparatus, the circuit 7 will be opened and closed alternately a number of times corresponding to the figure in question of the subscribers number. The relay Rt Fig. 4 will thus be de-ene-rgized a corresponding number of times. The first opening of the circuit 7 causes a circuit 20 to be closed through the relay R11 Fig. 5,

which then energizes and operates the-register controller PRO so as to cause the latter to be advanced another step, whereby the buzzer circuit is disconnected. At the same time a circuit 21 is closed through the holding magnet RE of the first register switch, whereby said switch is advanced one step. YVhen the impulse circuit is again closed, the circuits 20 and 21 are opened, whereby the first register switch RE will be advanced another step, while the slow acting relay Ii-R Fig. 5, keeps its armature attracted,

thereby maintaining the register controller PRO in the position in which the register switch RE is connected up. It is now readily understood that each of the following impulses will advance the register switch RE two further steps. After the first impulse series has been sent out, the relay RS Fig. 4, will be maintained energized long enough to allow the relay RR Fig. 5, to deenergize, whereby the register controller PRO is advanced another step. In this position of the register controller a circuit 22 is closed through the clutch magnet of the sequence switch MR, whereby the sequence switch is advanced into its third position in which a circuit 23 is closed through the holding magnet R of the first group selector RV Fig. 4. The group selector w ll, conse- 'lay RS Fig. 4, will be de-energized t 'quently, be advanced one step thus closing a 'another step forward. In this new position of the selector the circuit 240i the relay RR- Fig. 5, is again opened and, consequently, the circuit 25 will also be opened causing the register switch RE to take another step forward. At the same time, however, the circuit 23 is again closed causing the group selector to takp another step forward and to close once more the circuit 24. When, as a consequence, the relay RR again energizes, the register switch RE will receive another current impulse so as to be advanced one step more, while at the same tlme the circuit 23 is opened, causing the group selector to take another step forward.

In this way the group selector and the register switch will be advanced step by step while mutually controlling each other in such a way, that the group selector cannot take another step forward, untilthe control relay of the register switch has been energized or de-energize-d respectively "to move the register switch-a corresponding step for-- ward. In the meantime the slow-acting relay Rs Fig. 4, is kept energized by the repeated impulses sent through the circuit 18 and the corresponding contacts in every second position of the group selector.

When the register switch RE moves into its last position following immediately after the numerical position designated by the numeral 0, a circuit 26 will beclosed over a contact of the relay BB which is now energized and through the holding magnet R of the group selector. The magnet last mentioned, which just before received a current impulse over the circuit 23, will therefore be prevented from releasing its armature and the group selector will, consequently, be maintained in the corresponding position, which is a position located between two adjacent numerical positions.

At the same time as the register switch RE, reaches its last position, also a circuit 27 is closed throu h the holding magnet IM of the secon ar register controller SRO said controller being then advanced into its second position thereby opening the circuit 25 of the register switch. After the switching operation having thus been stopped, while the group selector is in an intermediate position, the slow-actin reis.- by closing a circuit 28, whereby the sequence switch SOGr is advanced intoits fifth position, The circuit 24 of'the relay RR Fig. 5, is then opened and, upon the de-energization of said relay, the circuits 26 and .27 will be opened. The register controller SRO will thus be moved into the next position in which the holding magnet R of the roup selector again receives current over tlie contact K whereby the group selector is maintained in the intermediate position in question. The register controller SRO, Fig. 5, however, will now receive another current impulse over the circuit 29, whereby it is advanced another step. In this moment, if the second register switch -RE, has not yet received all current impulses from the subscriber, the register controller SRO will be retained in the position it is now occupying, through a circuit 30 over contacts of the register controller PRO. As soon as the second register switch has received all the impulses, the primary register controller PRO will, however, be operated in the manner previously described so as to disconnect the register switch RE, and to connect up instead of it the third register switch RE for receiving the next series of impulses from the subscriber. The circuit 30 is then also opened and the secondary register controller SRO will, as a consequence, take another step forward thereby opening the circuit of the holding magnet of the group selector. The group selector will therefore be advanced another step and will thus be moved into the numerical position corresponding to the selected group of junction lines FL,. Supposing the first register switch RE having been set on the numerical position 7, the group selector Wlll. now occupy the position designated by the numeral 8.

l/Vhen the group selector moves into the position last mentioned, a circuit 31 is closed through the clutch magnet KM for all junction finders S,, Fig. 6, which are disengaged at the time and said junction finders will thus be started. The junction finder which first finds the junction line FL in question closes a circuit 32 including the relay RS,, Fig. 4, at the group selector RV and a relay RG Fig. 6, pertaining to the grou selector in question. The relay last mentioned energizes and locks itself over a contact 33 while short-circuiting a resistance whereby the junction line FL, is marked as engaged. At the same time the clutch magnet of the junction finder is disconnected and the junction finder will thus be stopped. The relay RS Fig.4, closes a circuit 34 thereby causing the sequence .switch SOG, to be moved into the sixth last mentioned attracts its armature, the clutch ma net KM, of the sequence switch SOG, receives another impulse over the circuit 37 whereb the sequence switch is moved into its t ird position. In this position the group selector RV, will now be connected up to the talking line branches of the junction line FL, a circuit 38 being then closed through the holding magnet R, of the group se ector overthe b-branch of the talking line. As a consequence, the group selector RV, is advanced one step and a circuit 39 is closed over the a-branch of the talking line through the control relay RR,, Fig. 5, of the register equipment said relay in turn closing a circuit 40 through the holding magnet RE, of the second register switch, whereby said switch is advanced one step. At the same time, however, the relay RR, opens the circuit 38 of the holding magnet R, of the group selector so as to cause the group selector to be .advanced another step. The setting of the second group selector RV, will then proceed alternately with the setting of the register switch RE, in the same way as above described with reference to the first group selector RV and the register switch RE until the register switch RE, reaches its end position, when a circuit 41 is closed through the holding magnet R, of the group selector RV,. The group selector will thereforebe retained in the corresponding intermediate position in spite of the control relay RR Fig. 5, being energized in this position thus keeping the circuit 38 open. As the relay RG,, Fig. 6, will no longer receive current impulses from the group selector, it releases its armature and closes a circuit 42, whereby the sequence switch SOG, is advanced into its fourth position. In this position a circuit is now closed which corresponds to the circuit 31 above described and whereby the junction finders of the second group selecting section (not shown in the drawings) are started similarly as the junction finders S of the first group selecting section, the junction line FL, being thus similarly connected to the junction line lead- .ing to the third group selecting section.

The circuit arrangement for the junction finders of the second group selecting section as well as the third group selector and the appertaining sequence switch (likewise not shown) is identical with that shown in Fig. 6. The setting of the third group selector will therefore be effected identically in the same way as described with reference to the second group selector RV,, Fig. 6. After the setting of the third group selector has been completed, a circuit l3 will be closed in the same way as above described with reference to Fig. 6. Said circuit actually passes over the third group selector and the appertaining sequence switch not. shown, but

its course will appear from Fig. 6 in which the corresponding circuit is deslgnated w1th.

the same reference numeral. The circuit 43 in question will cause all junction finders S Fig. 7, of the third group selecting section which are disengaged at the time, to be started. That one of the junction finders S thus started which first finds the junction line in question, will close a circuit 44 including a relay RV Fig. 7, which locks 1tself over itscontact 45, and the relay RG Fig. 6, which now again energizes and closes a circuit 46, whereby the sequence switch SOGr or the'corresponding sequence switch of the third group selecting section respectively is advanced into the fifth position in which the talking line is switched on to the line selecting section. v

At the same time'as the junction-finder S is stopped b the energization of the relay'RV Fig. the sequence switch SOV Fig. 7, is advanced into its second position by a current impulse over the circuit 47. In this position a circuit 48 is closedthrough the clutch magnet KM, of the selector finders LVS accessible at the time and said selector finders are thus started. The finder which first finds the junction. line FL in question, closes a circuit 49 through a relay RV Fig. 8, which looks itself over acontact 50 at the same time connecting a relay RV -in circuit over its contact 51. The relay RV closes a circuit 52 whereby the sequence switch SOV, Fig; 7, is advanced into the third position. In this position a circuit 53 is closed over the b-branch of the talking line and through a relay RV, which operates to open said circuit 52 thereby causing the sequence switch to be stopped in its third position. Just before the relay RV closes a circuit 54 through the clutch magnet KM of the sequence switch MRV,

whereby the latter is moved into its second position. At the same time the relay RV closes a circuit 55 through a slow-acting relay RV corresponding in respect of its action to the relay RS Fig. 4. The relay RV closes the circuit of a relay RV,

which connectsitself ina holding circuit' 57 .The relay RV also closes a circuit 58 through the holding magnet V of the tenth selector'Lv As a consequence, this selector is advanced one step. A circuit 59 is then closed over the a-hranch of the talking line through thecontrol relay RR Fig- 5,

of the register equipment. Said relay, in operating, closes a circuit 60 throughthe holding magnetof the register switch RE whereby the latter is advanced one step." At the same time as the control relay RR Fig. 5. energizes, the circuit of the relay RV is opened and, as a consequence, the circnit58 of the holding magnet V of the tenth selector is also opened, whereby the tenth. selector is moved one Step further,

quence, it will release its armature. The.

circuit,58..of the holding magnetof the tenth selector isth'enfopened andthe tenth selector takes another step forward into the numerical position corresponding to thefigure in question on the subscribers number. At the same time a circuit 62 is closed. through a relay RV, which looks itself over a circuit 63 and prepares the connecting up of the holding magnet V of the unit selector LV the circuit 64 of said mag net being closed when the relay RV. which is now energized over a circuit 65, again attracts 1ts armature. As a consequence, the unit selector Wlll be advanced one step,

whereby. a circuit 66 is closed over the a-- branch through the control relay RR Fig. 5, which in turn closes a circuit 67 through the register switch R1 1 the latter being thus advanced one step. At the same time the relay-RR opens the circuit 61 of the relay RV Fig. 8, which-in turn opens the circuit of the holding magnet of the unit selector, whereby the latter is advanced into the next position in which said circuit 66 of the control relay RR is again opened with the same result as previously stated. The setting ofthe unit selector will proceed, until the register switch RE reaches'its end position, in which a circuit 68 is closed,

whereby the unit selector is retained-in an RV which then connected itself into a holding circuit 70. hen the relay RV new again releases its armature. a circuit 71 is closed, including a relay RV,. The relay last mentioned locks itself over its contact 72 at the same time closing a circuit 73 of r. relay RV which in turn closes a circuit 74 of a tenth relay RV corresponding to the tenth group to which the desired subscriber belongs. Atthe same time a circuit 75 is closed through the clutch magnet KM Fig. 7, of the connector S the latter being then started to search the subscribers line in question. When the. cennectorreaches this line, a circuit 76 is closed through a relay RV,,, Fig. 8, which opens the circuit 75, thereby causing the connector to be sto ped. At the same time a circuit 77 is c osed through the clutch magnet KM Fig. 7, of the sequence switch SOV. Sup osing the desired subscribers line being isengaged, the sequence switch will. then be advanced into the fifth position while passing the fourth position in which a testing of the subscribers line takes place. In passing the fourth position, a circuit 78 is closed through a relay RV and the cut off relay BR, Fig. 3. of the desired subscribers line. The relay RV locks itself over a circuit 79 at the same time marking the desired sub scribers line as en a ed b short-circuitin h a resistance V In the fifth position of the sequence switch a circuit 80 is closed whereby the sequence switch is advanced into the sixth position from which the sequence switch will be successively advanced into the ninth position by current through a circuit 81. In passing the sixth, seventh and eighth positions a continuous calling signal is being sent out from a source of calling current RH over acircuit 82. In the ninth position of the sequence switch, on the other hand, an intermittent calling signal is sent out from a source of calling current RH over the contact 83, the signal last mentioned remaining, until the subscriber removes his receiver to answer the call. The calling current passes through a slow-acting relay RV which, however, is adapted not to be operated by the calling current. On the other hand, it will be operated, when the called subscriber removes his receiver, as the relay RV will then be passed by current from the central battery. The calling signal sent to the called subscriber may be heard in usual way by the calling subscriber by a buzzer signal eing sent over contacts 84 and 85 of the sequence switch from sources of signal current SU. SU through a primary winding SL of a transformer T the secondary windings of which are connected to the talking line branches.

Vhen the relay RV energizes, the se quence switch receives a current impulse over the circuit 86, whereby the sequence switch is advanced into the tenth position in which the talking connection is completed and the sources of signal current are disconnected.

Before the called subscriber answers, the microphone circuit of the called subscriber has been prepared in the following way. \Vhcn the register switch RE Fig. 5, reaches its end position, a circuit 87 will be closed simultaneously with the closure of the circuit 68, whereby the secondary register controller SRO is moved into its last but oneposition and, upon the relay RR, de-energizing, it will finally be moved into its last position, in which a circuit 88 is closed through the clutch magnet KM, of the sequence switch MR. The latter will then be returned into its initial position, thereby causing the contact arms of all register switches and register controllers to be restored into normal position the 'circuits 14 and 10 are then opened whereby the relays RR Fig. 5, and RS Fig. 4, are de-energized. Finally, also the relay RS Fig. 4, is de-energized, whereby a circuit 89 is closed, causing the sequence switch SOG, to be advanced into its seventh position, in which the microphone battery of the called subscriber is connected up through two inductive resistances RS and R8,. The resistance RS forms the winding of a relay which will thus energize, when the called subscriber answers. A circuit 90 is then closed, whereby the sequence switch SOGr is advanced into its eighth position. lVhen the relay RS energizes, also the disconnecting relay RS receives current over a circuit 91. In the eighth position the sequence switch SOGr also a circuit 92 is closed including the subscribers meter SM, Fig. 1, which will thus register the call.

The restoring of the tenth and unit selectors is effected in the following way. In the fifth position of the sequence switch SOV, Fig. 7, the circuit 49 of the relay RV Fig. 8, is opened, whereby this relay as well as the relay RV are de-energized. A circuit 93 is then closed through the clutch magnet of the sequence switch MRV, whereby this sequence switch is returned to the initial position, said sequence switch, in returning to normal position, carries with it the contact arms of the tenth and unit selectors, which are thus also returned to normal position.

The group selectors RV and RV will remain during the conversation in the position to which they have been previously setand, as a consequence, the circuits 32 and 44 are kept closed over the corresponding c-wires, for the purpose of maintaining the talking connection.

After both subscribers having restored their receivers at the end of the conversation, the disconnecting relay RS Fig. 4, will be de-energized the circuit 6 being thereby opened, causing the relays BR, ER and GR,

Fig. 3, to be tie-energized. Further, the relay RS closes a circuit 94, whereby the sequence switch SOG Fig. 4, is returned to normal position. At the same time the contact arms of the group selector RV are carried back into normal position by the action of the sequence switch. The circuit 32 is now opened, whereby the relay RG Fig. 6, is de-energized, and, as a consequence, a circuit 95 will be closed, whereby the sequence switch SOG is restored to normal position, carrying. with it the contact arms of the group selector RV which are thus returned into normal position. The circuit 44 is then opened, whereby the relay RV Fi 7 is de-energized and a circuit 96 is close causing the sequence switch SOG to be restored to normal position.

I11 case the called subscribers line should be engaged, the circuit 78 of the relay BV Fig. 7, will not be closed in the fourth posi-- tion of the sequence switch SOV and the seuence switch will therefore be stopped in t is fifth position. In this'position the callingsubscriber will receive a buzzer signal from a source of buzzer current SU over a contact 97 ot' the sequence switch. When the calling subscriber restores his receiver, the diii'erent switches will be restored and the connection will be severed in the same way as above described.

I claim:

1. In a telephone exchange system the combination with a selector and a registering and controlling device, of a selector circuit, means associated with the registering and controlling device for sending impulses over said circuit for the setting of the selector, a register circuit, means associated with the selector for sending back impulses over said register circuit for the setting of the registering and controlling device, said circuits being arranged to control one another mutually so as to cause the impulses to be sent alternately over the selector circuit and the register circuit respectively, and means associated with the registering and controlling device; for stopping the selector in a predetermined position.

2. In a telephone exchange system. the combination with a selector and a registering and controlling device, of a selector circuit, means associated with the registering and controlling device for sending impulses over said circuit for the setting of the selector, a register circuit, means included in said selector circuit for sending back impulses over said register circuit alternately with impulses over said selector circuit for the setting of the registering and controllin device, and means associated with the registering and controlling device for stopping the selector in a predetermined position.

3. In a telephone exchange system the combination with a selector and a registering and controlling device, of a selector circuit, under the control of the registering and controlling device, a register circuit under the control of the selector, means included in said selector circuit and adapted to send back impulses from the selector to the registering and controllin circuit and adapted to send control impulses {from the registering and controlling device device for operating the latter, means 1nc uded in said reglster of the selector, and means associated with .the registering and controlling device for ing and controlling device and responsiveto' said back impulses for sending control impulses over said selector circuit to operate the stepping magnet of the selector, and means associated with the registerin and controlling device for stopping the se ector in a predetermined position. i

5. In a telephone exchange system thecomb-ination with a selector and a registering and controlling device, of a selector circuit, under the control of the registering and controlling device, a register circuit under the control of the selector, a stepping magnet of the select-or included in said selector circuit and controlling said register circuit so as to send-back impulses to the registering and controlling device over the register circuit, a stepping magnet of the registerin and controlling device responsive to said back impulses andcontrollin the said selector circuit so as to send control impulses over the selector circuit to operate the step ping magnet of the selector and means associated with the registering and controlling circuit so as to send back impulses to the registering and controlling device over the register circuit, a relay responsive to said back impulses and controlling the said selector circuit so as to send control impulses over the selector circuitto operate the stepping magnet of the selector, a relay circuit controlled by said relay and including a. stepping magnet of said registering and controlling device, and means associated with the registering and controlling device for stopping the selector in a predetermined position.

"7.. In a telephone exchange system the combination of a selector having a stepping magnet I and an escapement mechanism adapted to cause the selector to be stepped forward one step upon the energization of the stepping ma et and another step upon the de-energizatlon of the steppingmagnet, a selector circuit including said stepping magnet, a registering and controlling device, a register circuit for operating said registering and controlling device controlled by said stepping magnet so as .to be closed and opened res ectively in every second postion of the se ector, means associated w1th said registering and controlling device and operating in response to the current impulses in said register circuit to send control impulses through said selector circuit for operating the stepping magnet of the selector.

8. In a telephone exchange system the combination of a selector havmg a stepping magnet and an esca ement mechanism adapted to cause the se ector to be stepped forward one step upon the energization of the stepping magnet and another step upon the de-energization of the stepping magnet, a selector circuit including said stepping magnet, a registering and controlling device comprismg a number of register switches having a stepping magnet and an escapement mechanism adapted to cause the register switch to be stepped forward one step upon the energization of the stepping magnet and another step upon the de-energization of the stepping magnet, a register circuit for operatlng the registering and controlling device controlled by the stepping magnet of the selector so as to be closed and opened respectively inevery second position of the selector, means associated with said registering and controlling device and operating in response to the current impulses in said register circuit to send control impulses through said selector circuit for operating the stepping magnet of the selector, and means associated with the registering and controlling device for stopping the selector in a predetermined position.

In testimony whereof I aflix my signature.

NILS GUNNAR PALMGREN. 

